Technical Field
-
The invention relates to a composite material that uses
a triaxial woven fabric including, for instance, a prepreg in
which a resin is not completely cured, and a molded body made
of the composite material, in particular, to a composite
material that is light in weight, large in the mechanical
strength and endowed with the electrical conducting properties,
the electrical insulating properties, the heat conducting
properties and the heat insulating properties, a molded body
and prepreg.
Background Art
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In composite materials that are used in existing
structured bodies, reinforcement fibers are impregnated with
a resin. In the following, such composite materials are
referred to as "fiber-reinforced resin composite materials".
-
In the fiber-reinforced resin composite material,
combinations of reinforcement fibers and resins to be a matrix
can be properly selected.
-
Accordingly, the fiber-reinforced resin composite
materials can be endowed with the physical and chemical
properties that are appropriate for service conditions
thereof.
-
As a result, the fiber-reinforced resin composite
materials are used in many application fields.
-
Furthermore, the fiber-reinforced resin composite
materials are high in the specific strength and excellent in
the corrosion resistance. Accordingly, the fiber-reinforced
resin composite materials are suitable for structured bodies
that are light in the weight and subjected to large stress,
resulting in finding applications in many fields.
-
As a molded body that uses the fiber-reinforced resin
composite material, there is an antenna's structural material
for use with an artificial satellite.
-
For instance, JP-A-11-168321 discloses a planar antenna
device.
-
In the planar antenna device, metal radiation elements
are arranged on a thin film (first film) of KFRP (Kevlar (Trade
mark) fiber-reinforced plastic).
-
The above Kevlar belongs to aramid fiber.
-
In front of the first film, a KFRP film (second film)
is similarly disposed so as to face the first film.
-
The second film is provided with a ground conductor metal
film such as a metal film and so on.
-
The first film is used as a radiation element sheet and
the second film is used as a ground conductor sheet.
-
The first film and the second film are expanded into
planes by use of an expansion mechanism.
-
The expanded first film and second film constitute a
planar antenna.
-
An existing planar antenna configuration will be
explained with reference to Fig. 4. Fig. 4 is a schematic
diagram of an existing planar antenna.
-
The configuration of the existing planar antenna, as
shown in Fig. 4, is provided on a KFRP film 401 with circular
patches 405 to be metal elements.
-
Furthermore, in a ground conductor film 404 of the
existing planar antenna, a metal film or fibers made of a metal
such as copper are formed tissue-like as if straining paper.
-
In the existing planar antenna configuration, the KFRP
film 403 is provided with the ground conductor film 404.
-
Furthermore, the KFRP films 401 and 403 are adhered and
fixed to a frame-like dielectric material (frame-like member)
402 made of CFRP (carbon fiber-reinforced plastic) and expanded
into planes by use of an expansion mechanism.
-
Thus, the existing planar antenna, by supporting the
metal elements and the ground conductor layer with the
expansion mechanism such as the CFRP frame member and so on
and the films such as the KFRP, accomplishes lighter weight.
-
However, in a reflector (antenna reflector) of the
antenna, different from the planar antenna, a conductive layer
has to be expanded with a definite shape.
-
Furthermore, depending on the application circumstances,
the antenna reflector itself is demanded to have sufficient
mechanical strength.
-
Still furthermore, depending on the application
circumstances, the antenna reflector is demanded to have
spring-back properties with which the antenna reflector can
restore its original state even after temporarily deformed
owing to load stress and so on.
-
Accordingly, in the application to the antenna reflector
and so on, a structure in which metal fiber tissue is provided
to the KFRP film, being deficient in the self-sustaining
properties because of being film-like or sheet-like, cannot
function.
-
Accordingly, in the antenna, the fiber-reinforced resin
composite material is molded into a three-dimensional curve
such as a paraboloid, and thereby the reflector is constituted.
-
However, the antenna, in order to form an electromagnetic
wave reflection surface, has to be endowed with the electrical
conducting properties.
-
Accordingly, in the existing antennas, such structures
as that in the triaxial woven fabric itself, as the
reinforcement fiber of the composite material that constitutes
the three-dimensional curved surface, conductive carbon fiber
is used, or plating is applied on a surface of the molded body
made of the composite materials, or a metal foil is laminated
are adopted.
-
However, when the carbon fiber is used in the triaxial
woven fabric as the reinforcement fiber of the composite
material, the carbon fiber that is high in the electric
conductivity, being high in the elastic modulus, is difficult
to weave and mold, resulting in pushing up the manufacturing
cost.
-
Furthermore, when the carbon fiber is used in the
triaxial woven fabric as the reinforcement fiber of the
composite material, the carbon fiber that is high in the
electric-conductivity, being at most 1.9 x 10-4 Ω·cm in the
volume resistivity, is not sufficient in enhancing the
electromagnetic wave reflectance or in coping with higher
frequencies.
-
Still furthermore, the antenna has a very large dimension
and shape in a molded state. Accordingly, also when a surface
of the composite material that is shaped into the antenna is
plated, irrespective of wet or dry process, there is
restriction on a magnitude of a processing bath or chamber,
and the adhesion of the plating can be uniformly applied with
difficulty.
-
Furthermore, when the plating is carried out according
to a wet process, a plating liquid unfavorably erodes the
composite material or is absorbed by the composite material.
-
Still furthermore, when the metal foil is stuck onto a
surface of the molded composite material, since, in an
artificial satellite antenna reflector or the like that is
finished very light in the weight, a molded body is very thin,
even owing to only a slight stress generated on a surface
thereof, warp is caused and deformation results, or when
adhesive force is suppressed to inhibit the deformation from
occurring, the metal foil peels off.
-
Furthermore, when an artificial satellite is launched,
a very high-energy acoustic vibration due to a boost gas that
accompanies a shock wave of a rocket is transmitted even to
the inside of a fairing where the antenna is housed.
-
Accordingly, in the artificial satellite antenna, the
surface of the metal foil is in some cases broken. When in
order to inhibit the metal foil surface from breaking, a
thickness of the metal foil is larger, the heavy weight results .
-
In addition, the metal foil originally has a
two-dimensional plane and, when being stuck to a
three-dimensionally curved surface of the antenna, has no
conformability to the curved surface. Accordingly, it is
difficult to form a three-dimensional antenna with a single
metal foil.
-
Furthermore, when metal foils that are divided and cut
in conformity with a three-dimensional shape are stuck together
and thereby a three-dimensionally curved surface is formed,
since an adhesive remains between stuck surfaces, the metal
foils cannot be stuck with the electric conductivity
maintaining.
-
In order to cope with such problems, although it has been
tried to constitute the antenna with a non-woven fabric made
of metal fibers, non-woven metal fabric alone, being low in
both the mechanical strength and the elastic modulus, cannot
work as a structural material in this application.
-
On the other hand, in a molded body that is used in, for
instance, space, other than the electrical conducting
properties, for instance in the case of an antenna, the heat
conducting properties in a thickness direction, the electrical
insulating properties, and the heat insulating properties are
also demanded. However, it is difficult for the existing
material to give these characteristics.
-
The invention is carried out in view of the above problems
and intends to provide a composite material that has the
mechanical strength, the elastic modulus and high specific
strength that are similar to that of the fiber-reinforced resin
composite material, and at least any one of the electrical
conducting properties comparable to metal materials, the
electrical insulating properties, the heat conducting
properties and the heat insulating properties, a molded body
and a prepreg.
Disclosure of the Invention
-
In a composite material according to the invention, at
least one or more triaxial woven fabrics and at least one or
more non-woven fabrics are laminated, thereby a laminated body
is formed, and the laminated body is impregnated with a resin.
-
Furthermore, in a composite material according to the
invention, at least one or more triaxial woven fabrics
impregnated with a resin and at least one or more non-woven
fabrics impregnated with a resin are laminated.
-
Still furthermore, in a composite material according to
the invention, at least one or more triaxial woven fabrics
impregnated with a resin and at least one or more non-woven
fabrics are laminated.
-
Furthermore, in a composite material according to the
invention, the triaxial woven fabrics and the non-woven fabrics
are alternately laminated.
-
Still furthermore, in a composite material according to
the invention, the resin is in a not completely cured state.
-
Furthermore, in a composite material according to the
invention, the non-wove fabric has the electrical conducting
properties.
-
Still furthermore, in a composite material according to
the invention, the non-woven fabric has the electrical
insulating properties.
-
Furthermore, in a composite material according to the
invention, the non-woven fabric has the heat conducting
properties.
-
Still furthermore, in a composite material according to
the invention, the non-woven fabric has the heat insulating
properties.
-
Furthermore, in a molded body according to the invention,
at least one or more triaxial woven fabrics and one or more
non-woven fabrics are laminated, thereby a laminated body is
formed, the laminated body is impregnated with a resin, thereby
a composite material is formed, the composite material is
laid-up in a mold in a state where the resin is not completely
cured followed by curing the resin of the laid-up composite
material, and thereby a molded body is formed.
-
Still furthermore, in a molded body according to the
invention, at least one or more triaxial woven fabrics
impregnated with a resin and at least one or more non-woven
fabrics impregnated with a resin are mutually laminated in a
state where the resins are not completely cured and thereby
a composite material is formed, the composite material is laid
up in a mold followed by curing the resin in the laid-up
composite material, and thereby a molded body is formed.
-
Furthermore, in a molded body according to the invention,
at least one or more triaxial woven fabrics impregnated with
a resin and at least one or more non-woven fabrics are laminated
in a state where the resin of the triaxial woven fabric is not
completely cured and thereby a composite material is formed,
the composite material is laid up in a mold followed by curing
the resin in the laid-up composite material, and thereby a
molded body is formed.
-
Still furthermore, in a molded body according to the
invention, at least one or more triaxial woven fabrics and at
least one or more non-woven fabrics are laminated to form a
laminated body, the laminated body is laid up in a mold with
the laminated body impregnating with a resin followed by curing
the resin in the laid-up laminated body, and thereby a molded
body is formed.
-
Furthermore, in a molded body according to the invention,
a triaxial woven fabric impregnated with a resin and a non-woven
fabric are laminated and thereby a laminated body is formed,
the laminated body is laid up followed by curing the resin,
and thereby a molded body is formed.
-
Still furthermore, in a molded body according to the
invention, the non-wove fabric has the electrical conducting
properties.
-
Furthermore, in a molded body according to the invention,
the non-woven fabric has the electrical insulating properties.
-
Still furthermore, in a molded body according to the
invention, the non-woven fabric has the heat conducting
properties.
-
Furthermore, in a molded body according to the invention,
the non-woven fabric has the heat insulating properties.
-
Still furthermore, in a prepreg according to the
invention, triaxial woven fabrics of reinforcement fiber and
conductive non-woven fabrics are alternately or in an arbitrary
order laminated followed by impregnating with a resin, and
thereby a prepreg is formed.
-
Furthermore, in a prepreg according to the invention,
prepregs formed by impregnating triaxial woven fabrics of
reinforcement fiber with a resin and prepregs formed by
impregnating conductive non-woven fabrics with a resin are
alternately or in an arbitrary order laminated, and thereby
a prepreg is formed.
-
Furthermore, in a composite material according to the
invention, the above prepregs are mutually laminated or the
above prepreg is laminated with a prepreg having another
structure.
-
Still furthermore, in a composite material according to
the invention, triaxial woven fabrics made of reinforcement
fiber and conductive non-woven fabrics are alternately or in
an arbitrary order laminated followed by impregnating with a
resin and further followed by curing, and thereby the composite
material is formed.
-
Here, a prepreg in the specification is one kind of
composite materials and is one (intermediate base material)
in which a fiber base material such as a triaxial woven fabric,
a unidirectional material and a biaxial fabric is impregnated
with a resin and the resin is maintained in a semi-cured state
(a state that is not completely cured).
-
Furthermore, in the specification, as methods and
conditions of curing the prepreg, as one example, the following
methods and conditions can be used.
-
The composite material prior to the curing according to
one example of the following methods and conditions is a
prepreg.
(Method)
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1. Compression molding, 2. Vacuum bag molding, 3.
Autoclavemolding, 4. Fiber placement molding, 5. Sheet winding
molding, 6. Rolling table molding and so on.
(Conditions)
-
Curing temperature: 120 to 180 degree centigrade.
Curing time period: 1 to 3 hours.
Molding pressure: atmospheric pressure to 0.6 MPa.
-
Furthermore, "lay-up" means an operation by which the
fiber base material or prepreg (is cut, stuck and laminated)
is given a shape on a mold.
-
Still furthermore, a non-woven fabric is one in which
short fibers are entangled and formed into a sheet. Paper,
felt and absorbent cotton can be said as one of the non-woven
fabrics.
-
As the characteristics of the non-woven fabric, it can
be cited that the non-woven fabric is physically
pseudo-isotropic.
-
That is, since the non-woven fabric can well conform to
a three-dimensionally curved surface and a shape having a sharp
angle portion, wrinkle is caused with difficulty. Furthermore,
the non-woven fabric, in the case of being laminated with the
other material, can be peeled with difficulty. This is evident
in the thermal shock test and the peel test.
-
Furthermore, the non-woven fabric, after folding, leaves
a fold line with difficulty, and after expansion, its function
does not disappear.
-
Still furthermore, the non-woven fabric, having voids
in comparison with the metal foil or the like, is low in the
density, resulting in lighter weight.
-
Furthermore, the non-woven fabric, having voids, can
withstand sound or vibration at the launch of a rocket,
resulting in neither breaking nor peeling.
-
Still furthermore, the electrical conducting properties
and the heat conducting properties of the non-woven fabric,
in the case of the metal fibers being used or the metal plating
being applied, reflect the characteristics of the metal.
-
Thus, when the electrical conducting and heat conducting
non-woven fabric is used in the composite material, the
invention exhibits the following effects.
-
So far, carbon fiber composite materials, being high in
the elastic modulus, light in the weight, very small in the
thermal expansion coefficient, and high in the heat conducting
properties in a fiber length direction, have been used in almost
all members of an artificial satellite.
-
However, because the heat conducting properties in a
direction perpendicular to a fiber axis of the carbon fiber
are low and the heat conducting properties of the matrix resin
are very low, the heat conducting properties in a thickness
direction of the carbon fiber composite material are low.
Accordingly, the capacity of releasing heat in a thickness
direction is very low.
-
Here, a matrix resin means a resin for use in the matrix,
that is, a resin that becomes a matrix(base material).
-
Also in the reinforcement fiber, a resin called a sizing
agent is used. Accordingly, an ordinary resin and the matrix
resin are called differently. However, in general, a resin
of the composite material is a resin for use in the matrix.
-
The composite materials such as the fiber-reinforced
plastics (FRP) and polymer matrix composites (PMC), largely
divided, are made of three constituents.
- a reinforcement fiber.
- a matrix(base material): a resin in the case of the
PMC.
- an interface between the reinforcement fiber and the
matrix.
-
In the case of the PMC, the matrix is a resin (polymer) ,
in the case of MMC (metal matrix composite), the matrix is a
metal, and in the case of CMC (ceramic matrix composite), the
matrix(base material) is ceramics.
-
When high heat dissipation from a thickness direction
can be obtained in the carbon fiber-reinforced composite
material, a heat dissipation structure of the artificial
satellite can be dispensed with or may be simplified.
-
That is, as in the invention, when the electrical
conducting and heat conducting non-woven fabric is used as the
non-woven fabric, the invention can contribute to the
artificial satellite in an improvement in the performance,
reduction in the weight and reduction in the cost.
-
In the invention where the electrically insulating and
heat conducting non-woven fabric is used in the composite
material, the composite material can be used like a printed
substrate (one in which a front surface and a rear surface are
fundamentally insulated).
-
Such composite material exhibits heat dissipation effect
in a mounted electronic device and an onboard device that
requires insulation.
-
Furthermore, in a composite material according to the
invention, by laminating the non-woven fabric to the triaxial
woven fabric, proper heat conducting properties (heat
dissipation properties) and heat insulating properties can be
given to necessary portions.
-
Accordingly, when the composite material according to
the invention is used in, for instance, a bus (body structure)
of an artificial satellite and a solar battery paddle thereof,
to portions where the heat control is necessary of these,
necessary heat control can be easily given by use of the
existing method.
Brief Description of the Drawings
-
- Fig. 1 is a schematic diagram showing one embodiment of
a composite material according to the invention,
- Fig. 2 is a partial enlargement diagram of a triaxial
woven fabric used in one embodiment of the composite material
according to the invention,
- Fig. 3 is a schematic diagram of an antenna reflector
as a molded body according to the invention, and
- Fig. 4 is a schematic diagram of an existing planar
antenna structure.
-
Best Mode for Carrying Out the Invention
-
In order to give more detailed explanation of the
invention, the invention will be explained in accordance with
the attached drawings. The explanation of an embodiment of
the composite material according to the invention can be also
applied to that of a prepreg according to the invention.
-
That is, in composite materials according to the
invention, one in which a resin of the composite material is
not completely cured is a prepreg.
(Explanation of one embodiment of composite material)
-
One embodiment of the composite material according to
the invention has a structure called a symmetrically laminated
structure that includes the non-woven fabric that is laminated
in an order of, for instance, triaxial woven fabric/non-woven
fabric/triaxial woven fabric, or non-woven fabric/triaxial
woven fabric/non-woven fabric.
-
Furthermore, when a plurality of the triaxial woven
fabrics is laminated, between arbitrary layers the non-woven
fabric may be interposed.
-
That is, in one embodiment of the composite material
according to the invention, the triaxial woven fabrics and the
non-woven fabrics may be arbitrarily laminated.
-
Here, the lamination means, irrespective of the kinds
of the layers, to stack two or more layers. In the invention,
the non-woven fabric layer is stacked onto the triaxial woven
fabric layer.
-
Furthermore, the non-woven fabric interposed between the
triaxial woven fabrics may not be sheet-like, that is, at least
one or more non-woven fabrics having an arbitrary shape such
as a circular, polygonal or elliptical shape may be interposed
between the triaxial woven fabrics.
-
Owing to such structure of the composite material,
thermal strain can be minimized, and furthermore when the
non-woven fabric is interposed between appropriate layers made
of the triaxial woven fabrics, higher density strength can be
obtained.
-
Furthermore, in one embodiment of the composite material
according to the invention, the triaxial woven fabrics of the
reinforcement fiber and the non-woven fabrics are laminated
alternately or in an arbitrary order followed by impregnating
with a resin.
-
In the composite material impregnated with a resin, when
the resin is not completely cured, it is a prepreg.
-
Furthermore, in one embodiment of a composite material
according to the invention, prepregs in which the triaxial
woven fabric is impregnated with a resin and prepregs in which
the non-woven fabric is impregnated with a resin may be
alternately or in an arbitrary order laminated.
-
When the composite materials are kept in the prepreg
state, by appropriately selecting combinations thereof,
composite materials having necessary
structures/characteristics can be formed.
-
Furthermore, in one embodiment of a composite material
according to the invention, a composite material having an
arbitrary shape may be formed by mutually laminating the
prepregs, or, as needs arise, by further laminating thereon
a prepreg having other structure, followed by curing.
-
Still furthermore, in one embodiment of a composite
material according to the invention, the triaxial woven fabrics
of reinforcement fiber and the non-woven fabrics are
alternately or in an arbitrary order laminated, impregnated
with a resin, cured, and thereby the composite material can
be obtained.
-
Here, as a method in which the triaxial woven fabric and
the non-woven fabric are laminated to obtain a composite
material, and therefrom a molded body is obtained, the
following variations can be considered. It goes without
saying that the invention is not restricted to the following
variations and even other methods can be used.
- 1. At least one or more triaxial woven fabrics and at
least one or more non-woven fabrics are laminated followed by
impregnating with a resin, and thereby forming a prepreg. The
prepreg is laid-up in a mold followed by curing, and thereby
a molded body is obtained.
- 2. A prepreg in which at least one or more triaxial woven
fabrics are impregnated with a resin and a prepreg in which
at least one or more non-woven fabrics are impregnated with
a resin are laminated. The obtained prepreg is laid-up in a
mold followed by curing, and thereby a molded body is obtained.
- 3. A prepreg in which at least one or more triaxial woven
fabrics are impregnated with a resin and at least one or more
non-woven fabrics (not impregnated with a resin) are laminated.
The obtained prepreg is laid-up in a mold followed by curing,
and thereby a molded body is obtained.
- 4. At least one or more triaxial woven fabrics and at
least one or more non-woven fabrics are laminated, laid-up in
a mold while impregnating with a resin followed by curing, and
thereby a molded body is obtained.
- 5. At least one or more triaxial woven fabrics are
impregnated with a resin, at least one or more non-woven fabrics
are laminated thereon followed by laying-up in a mold further
followed by curing, and thereby a molded body is obtained.
-
-
Furthermore, the lamination in a method in which the
triaxial woven fabric and the non-woven fabric are laminated
and thereby a composite material is obtained contains not only
a case where at least one or more triaxial woven fabrics and
at least one or more non-woven fabrics are arbitrarily
laminated but also a case where both are alternately laminated.
-
Here, as the method of impregnating with a resin, the
following methods can be cited.
- 1. A resin film is transcribed on a fiber base material
followed by compressing and heating to impregnate, and thereby
a semi-cured prepreg is obtained (it is called a dry (hot-melt)
method).
- 2. A fiber base material is impregnated with a resin
liquid followed by compressing and heating, and thereby a
semi-cured prepreg is obtained (it is called a wet
(impregnating) method).
-
-
Furthermore, when a molded body according to the
invention is generated, a prepreg (semi-cured intermediate
base material) process may be omitted.
-
That is, according to hand lay-up molding in which the
fiber base material and the non-woven fabric are directly
impregnated with a resin liquid in a mold followed by curing,
or autoclave molding in which a resin film is directly
transcribed onto a fiber base material and laying-up and
molding in an autoclave as it is further followed by curing,
a molded body can be obtained.
-
Furthermore, there is a method called an RTM molding in
which the fiber base material and the non-woven fabric are set
in a mold (it is called a preform) followed by injecting a resin
liquid and curing, and thereby a molded body is obtained.
-
Here, as one embodiment of a composite material according
to the invention, an example of a laminate structure of the
triaxial woven fabric and the non-woven fabric is shown in Fig.
1. Fig. 1 is a schematic diagram of one embodiment of the
composite material according to the invention.
-
In the composite material shown in Fig. 1, as the
non-woven fabric a conductive non-woven fabric is used. The
composite material shown in Fig. 1 has a sandwich-like
structure in which a conductive non-woven fabric 102 is
interposed between two triaxial woven fabric prepregs 101.
-
The triaxial woven fabric prepreg 101 is one in which
the triaxial woven fabric of reinforcement fiber is impregnated
with a resin. Furthermore, the resin with which the triaxial
woven fabric prepreg 101 is impregnated is not completely
cured.
-
The laminated bodies may be impregnated with a matrix
resin followed by molding into a target shape further followed
by curing.
-
Furthermore, in a weave structure of the triaxial woven
fabric, there are formed hexagonal through holes 201 that
interconnect a front and rear surfaces as shown in Fig. 2.
-
Accordingly, by controlling a magnitude of the through
holes 201 according to a weaving method of the triaxial woven
fabric, electrical conduction can be established between the
conductive non-woven fabrics disposed on the front and rear
surfaces of the interposed triaxial woven fabric. Fig. 2 is
a partially enlarged diagram of the triaxial woven fabric used
in one embodiment of the composite material according to the
invention.
-
In a structure of the composite material such as shown
in Fig. 1, by laminating an appropriate number of the triaxial
woven fabric prepregs 101 made of reinforcement fiber and the
non-woven fabrics 102, both the mechanical characteristics and
the electrical characteristics can be controlled and improved.
-
Furthermore, for instance, since there are the through
holes 201 of the triaxial woven fabricprepreg 101, for instance,
when the electrical conducting non-woven fabric is used as the
non-woven fabric, the composite material can be provided with
the electrical conducting properties in a thickness direction
thereof.
-
Here, the thickness direction means a direction
substantially vertical to a sheet surface of the triaxial woven
fabric prepreg 101 shown in, for instance, Fig. 1.
-
Accordingly, in the case of a molded body that uses the
composite material shown in, for instance, Fig. 1, excellent
electrical conducting properties can be established even in
a thickness direction thereof.
-
Furthermore, for instance, since there are through holes
201 of the triaxial woven fabric prepreg 101, for instance,
when the heat conducting non-woven fabric is used as the
non-woven fabric, the composite material can be provided with
the heat conducting properties in a thickness direction
thereof.
-
Accordingly, in the case of a molded body such an antenna
that uses the composite material shown in, for instance, Fig.
1, also in a thickness direction thereof, excellent heat
conducting properties can be established.
-
Furthermore, when an electrically insulating non-woven
fabric is used as the non-woven fabric, when the triaxial woven
fabric prepreg 101 is also provided with the electrically
insulating properties, the composite material shown in Fig.
1 itself can be insulated. Accordingly, when devices or
circuits are designed on the composite material, the designing
can be easily performed.
-
Still furthermore, when a heat insulating non-woven
fabric is used, according to a simple way, the composite
material can be endowed with the heat insulating properties.
Furthermore, in applications such as an antenna reflector, on
a surface side of the composite material made of the triaxial
woven fabric, when a conductive non-woven fabric is stuck
followed by laminating, and thereby preferable electrical
characteristics can be endowed.
-
Now, with reference to Fig. 3, a molded body (antenna
reflector) generated by use of one embodiment of the composite
material according to the invention will be explained. Fig.
3 is a schematic diagram of an antenna reflector as a molded
body according to the invention.
-
In the antenna reflector 301, an electrical conducting
non-woven fabric is stuck onto a front surface side of the
composite material made of the triaxial woven fabric followed
by laminating, and thereby the antenna reflector 301 is endowed
with preferable electrical characteristics.
-
In the triaxial woven fabric, owing to restrictions on
manufacture, there is a lower limit in making smaller an
opening.
-
The electric wave reflectance depends largely on a
magnitude of the opening, as the frequency becomes higher,
unless the opening is made smaller, the more the electric wave
goes through, resulting in lowering the electric wave
reflectance.
-
In order to cope with higher frequencies exceeding a
limit to the electric wave reflection due to the triaxial woven
fabric alone, a conductive non-woven fabric having
functionality higher in the electric wave reflectance is
laminated.
-
The non-woven fabric (functional non-woven fabric),
without damaging the characteristics of the triaxial woven
fabric, enables to enhance (or give) the functionality such
as the electrical, thermal performances.
-
Processes until a molded body is obtained from the fiber
base material such as the triaxial woven fabric will be
generally explained. As the method by which a molded body is
obtained from the composite material according to the
embodiment, there are, for instance, the following three
methods.
(Autoclave molding, vacuum bag molding)
-
1. Fiber base material → prepreg (impregnation ·
semi-curing) → lay-up (giving a form on a mold) → molding
(curing) → molded body.
(RTM molding)
-
2. Fiber base material → preform (setting in a mold)
→ molding (resin injection · curing) → molded body.
(Hand lay-up molding)
-
3. Fiber base material → lay-up (giving a form on a mold
with a resin impregnating · curing) → molded body.
[Characteristics of composite material]
-
In one embodiment of a composite material according to
the invention, the electrical characteristics such as the
electrical conducting properties, the electrical insulating
properties, the heat conducting properties, the heat
insulating properties and the electric wave reflecting
properties are controlled with the non-woven fabric.
-
That is, the electrical conducting properties, the
electrical insulating properties, the heat conducting
properties, the heat insulating properties and the electric
wave reflecting properties can be controlled with the kind of
the fiber given to the non-woven fabric, a filament diameter
of the fiber, and density (it is controlled by varying voids
and a thickness).
-
For instance, the heat conducting properties of one
embodiment of the composite material according to the invention
can be controlled with a material that is used in the non-woven
fabric. However, the electrical conducting non-woven fabrics
high in the electrical conducting properties are in many cases
the heat conducting non-woven fabrics high in the heat
conducting properties.
-
That is, the non-woven fabric that is used in the
composite material according to the embodiment can be
considered a heat conducting non-woven fabric, a heat
insulating non-woven fabric, an electrical conducting
non-woven fabric, an electrical insulating non-woven fabric,
a heat conducting and electrical conducting non-woven fabric,
a heat conducting and electrical insulating non-woven fabric,
a heat insulating and electrical conducting non-woven fabric,
and a heat insulating and electrical insulating non-woven
fabric.
-
According to the characteristics of these non-woven
fabrics, the characteristics of one embodiment of the composite
material according to the invention are determined.
-
Furthermore, to the acoustic vibration when a rocket is
launched, these non-woven fabrics, having voids therein
similarly to the triaxial woven fabrics, are light and can stand
up to stronger acoustic vibrations.
-
Still furthermore, as the structure and shape of the
non-woven fabric, for instance, in the electrical conducting
non-woven fabric, the non-woven fabric made of metal fiber or
metallized fiber, or the metallized non-woven fabric obtained
by depositing a metal on the non-woven fabric can take a
three-dimensionally free shape.
-
Accordingly, the non-woven fabric and the triaxial woven
fabric are laminated and, without completely curing the resin,
a prepreg can be formed.
-
Furthermore, the non-woven fabric and the triaxial woven
fabric can be laminated to form a composite material.
-
Still furthermore, to a composite material made of a
resin and the triaxial woven fabric, a non-woven fabric can
be stuck.
-
When a composite material that is formed into a
lamination structure by interposing the non-woven fabric
between the triaxial woven fabrics is molded, one that does
not warp and peel, can be superposed and pasted, and can be
formed into three-dimensional curved surfaces can be obtained.
Accordingly, disadvantages in the molding properties in the
metal foils can be overcome.
-
Furthermore, since the composite material
simultaneously works as a supporter of the non-woven fabric
and a structural material, large mechanical strength and
elastic modulus can be maintained.
-
A structure in which the triaxial woven fabrics and the
non-woven fabric are thus molded into one body is large in the
spring-back properties by which, even after temporarily bent
and deformed owing to application of load stress, when the
stress is removed, the structure restores its original shape.
-
The characteristics are very preferable in the antenna
reflector boarded on an artificial satellite and so on.
-
In addition, even when the prepreg of the triaxial woven
fabric impregnated with the resin is made extremely thinner
to an extent of a substantial film, its shape can be maintained
in space without the atmosphere. Accordingly, appreciably
lighter weights can be achieved.
(Embodiments)
-
In the following, a specific structure of a molded body
in which a composite material according to the invention is
employed will be explained as embodiments. Here, a parabolic
antenna reflector is adopted as a molded body according to the
invention. In addition, as the non-woven fabric an electrical
conducting non-woven fabric is used.
Embodiment 1
-
A sintered non-woven fabric in which copper fibers having
a filament diameter of 16 µm are used and that has the porosity
of 53.3% is pasted on a surface of a triaxial woven fabric
prepreg that is obtained by weaving 135tex glass fibers
according to a Basic weave with the weave density of 9.25
threads/inch and by impregnating with epoxy resin. With this
configuration, a reflector for use with a 350 mm diameter
parabolic antenna for use in 12 GHz frequency band is
experimentally prepared.
-
When a BS airwave of 11.84256 GHz is actually measured
through an amplifier with a spectrum analyzer, the receiving
intensity is -53.17 dB.
-
It is found that the reflector has such a light weight
as 31 g, different from a metal reflector, does not structurally
exhibit the plastic deformation due to an external load, has
the spring-back function and is excellent in the
shape-sustaining properties.
-
In the 180-degree peel test, material destruction of the
copper fiber sintered non-woven fabric does not accompany the
peeling.
-
In the thermal shock test from +180 degree centigrade
in an oven to -195 degree centigrade in liquid nitrogen, the
copper fiber sintered non-woven fabric does not peel off the
triaxial woven fabric composite material.
Embodiment 2
-
A sintered non-woven fabric in which stainless steel
fibers having a single fiber diameter of 8 µm are used and that
has the porosity of 18.2% is interposed between triaxial woven
fabric prepregs that are obtained by weaving 11tex PBO fibers
according to a Basic weave with the weave density of 18.5
threads/inch and by impregnating with cyanate ester resin.
With this configuration, a reflector for use with a 350 mm
diameter parabolic antenna for use in 12 GHz frequency band
is experimentally prepared.
-
When a BS airwave of 11.84256 GHz is actually measured
through an amplifier with a spectrum analyzer, the receiving
intensity is -53.57 dB.
-
It is found that the reflector has such a light weight
as 18 g, different from a metal reflector, does not structurally
exhibit the plastic deformation due to an external load, has
the spring-back function and is excellent in the
shape-sustaining properties.
-
In the 180-degree peel test, material destruction of the
stainless steel fiber sintered non-woven fabric does not
accompany the peeling.
-
In the thermal shock test from +180 degree centigrade
in an oven to -195 degree centigrade in liquid nitrogen, the
stainless steel fiber sintered non-woven fabric does not peel
off the triaxial woven fabric composite material.
Comparative embodiment 1
-
With 1 mm thick aluminum, a reflector for use with a 360
mm diameter parabolic antenna for use in 12 GHz frequency band
is experimentally prepared.
-
When a BS airwave of 11.84256 GHz is actually measured
through an amplifier with a spectrum analyzer, the receiving
intensity is -53.15 dB. It weighs 316 g.
Comparative embodiment 2
-
A copper foil having a thickness of 30 µm is pasted on
a surface of a triaxial woven fabric prepreg that is obtained
by weaving 135tex glass fibers according to a Basic weave with
the weave density of 9.25 threads/inch and by impregnating with
epoxy resin. With this configuration, a reflector for use with
a 350 mm diameter parabolic antenna for use in 12 GHz frequency
band is experimentally prepared.
-
In a draping pattern in which the copper foil is divided
into less than 12 divisions, the copper foils cannot fit well
into a three-dimensional curved surface, resulting in a
wrinkled reflector poor in a mirror surface accuracy.
-
It weighs 55 g, and after bending owing to own weight,
it cannot spontaneously restore its original shape through the
plastic deformation.
-
In the 180-degree peel test, the copper foil is peeled,
and it is found that the peel strength is such low as 0.093
kN/m or less.
-
With a sample after the thermal shock test, the peel test
is carried out. It is found that the peel strength is further
deteriorated to 0.056 kN/m or less.
Comparative embodiment 3
-
With a non-woven fabric simple body configuration in
which a non-woven fabric that uses aramid fibers having a single
fiber diameter of 12 µm and has the porosity of 17.3% is
copper-plated by a thickness of 5 µm followed by impregnating
with cyanate ester resin, a reflector for use with a 350 mm
diameter parabolic antenna for use in 12 GHz frequency band
is experimentally prepared.
-
Although since it is formed of the non-woven fabric
simple body, it weighs only 5 g, it is low in the tearing strength
and the stiffness, and deficient in the spring-back properties .
It is found that maintaining dimensional precision is
difficult.
-
In the above embodiments, as the electric conducting
non-woven fabric, the non-woven fabric made of copper fibers
and the non-woven fabric made of stainless steel fibers are
used, and as the composite material containing the triaxial
woven fabric, the glass fibers impregnated with epoxy resin
and PBO impregnated with cyanate ester resin are used. However,
the configurations of the composite materials according to the
invention are not restricted to the above.
-
As materials constituting the electrical conducting
non-woven fabric, metal fibers such as copper, silver, gold
and stainless steel fiber sintered non-woven fabrics (in order
to inhibit the performance from deteriorating owing to
corrosion of the metal, gold or silver may be formed according
to wet plating, vacuum-deposition or sputtering), or ones in
which fibers made of appropriate materials such as aramid, PBO,
glass, and carbon fiber are metal plated, or like a copper
plated aramid fiber non-woven fabric ones in which the
non-woven fabric made of aramid, PBO, glass or carbon fiber
is metal plated may be used.
-
Thus, the material of the fiber is not questioned when
the fiber has the electrical conducting properties and can be
formed into the non-woven fabric.
-
Furthermore, as the non-woven fabric, copper plated
aramid fiber non-woven fabric (weight: 38 g/m2, plating
thickness: 5 µm, porosity: 17%) can be used.
-
Such non-woven fabrics, in comparison with the non-woven
fabrics 100% made of the metal fibers, are lighter in weight,
higher in the mechanical strength, smaller in the thermal
expansion coefficient, less in deterioration in the
functionality after folding, easier in cutting, and can be
finished into an excellent cross section.
-
Furthermore, such non-woven fabrics, being highly
reflective even in a millimeter wave region, can be also applied
to, other than the reflector and the ground conductor, elements
such as patch and slot.
-
Furthermore, as the non-woven fabric, copper fiber
sintered non-woven fabric (weight: 50 g/m2, fiber diameter:
16 µm, porosity: 53%) can be used.
-
Such non-woven fabric, being 100% made of metal, is high
in the heat resistance, free from care of out-gassing, flexible
and small in the electrical resistance.
-
Furthermore, as the non-woven fabric, carbon fiber
non-woven fabric (weight: 10 g/m2, fiber diameter: 8 µm,
porosity: 27%) can'be used.
-
Such non-woven fabric, being carbon fiber, is electrical
conducting, and furthermore super-light in weight and small
in the thermal expansion coefficient.
-
When such non-woven fabric is combined with the triaxial
woven fabric in which the carbon fiber is used, with excellent
properties of the triaxial woven fabric maintaining as it is,
electric wave reflecting properties at higher frequencies can
be obtained.
-
Furthermore, in the embodiments, as the materials that
endow the molded body with the mechanical properties, an
example of the triaxial woven fabric made of the glass and PBO
fiber is cited.
-
The composite materials according to the embodiments are
common to the fiber-reinforced resin composite materials in
the mechanical properties such as the mechanical strength of
the molded body, stiffness and the spring-back properties that
enable to restore the original shape against the stress.
-
When the material of the molded body is properly selected,
the molded body can be tailored to applications.
-
In particular, the composite material made of a triaxial
woven fabric that uses continuous fibers is preferable.
-
In addition, when the molded body is formed into a
triaxial woven fabric structure, owing to the structural
symmetry thereof, the molded shape is deformed with difficulty
against the temperature variation and load of mechanical stress.
Furthermore, since when these loads are removed, the original
design shape can be restored, the shape stability is excellent.
-
As the fibers that can be used with the triaxial woven
fabrics, aramid, PBO, glass, and carbon fiber can be cited.
As the structure thereof, a 16 to 64 gage basic weave or bi-plain
weave pattern triaxial woven fabric structure can be adopted.
-
Furthermore, as the fibers that are used in the triaxial
woven fabrics, 64 gage basic weave pattern triaxial woven
fabric in which PBO fibers having the fineness of 11 tex
(weight: 26 g/m2, weave density: 18.5 threads/in) can be also
used.
-
The triaxial woven fabric, being made of the PBO fiber,
is high in the mechanical strength, high in the elastic modulus,
high in the heat resistance, negative in the thermal expansion
coefficient, electric wave-transmissive, such slender in the
fineness as 11 tex, such thin in a fabric thickness as 60 µm,
such super-light in the weight as 26 g/m2, and such high in
the weave density as 18.5 threads/in, resulting in higher
surface finishing accuracy and higher adherence with the
non-woven fabric.
-
Furthermore, since such triaxial woven fabrics can be
easily folded and the triaxial woven fabric simple body is
electric wave-transmissive, the physical properties are not
deteriorated owing to the folding.
-
Still furthermore, although as the matrix resin, epoxy
resin, cyanate ester resin and so on can be cited, the matrix
resin is selected according to the advisability of the
combination with the triaxial woven fabric and objects, and
is not necessarily restricted to these.
-
For instance, as the resin, high temperature curable
epoxy resin and cyanate ester resin (curing temperature: 180
degree centigrade, cure period: 2 hours, molding pressure: 0.6
MPa) can be used.
-
The resins used in the invention, when the molded body
is intended to use as, for instance, a space structure, are
ones that are suitable for a space environment, and when there
is no problem in the adherence, there is no particular
restriction.
-
A combination structure of the non-woven fabric and the
triaxial woven fabric may be any one of that in which the
non-woven fabric is pasted to the triaxial woven fabric, or
that in which the triaxial woven fabrics and the non-woven
fabric are laminated with the non-woven fabric interposed
between the triaxial woven fabrics.
-
Furthermore, triaxial woven fabrics made of two or more
kinds of different materials and the non-woven fabric may be
laminated with the non-woven fabric interposed between the
triaxial woven fabrics.
-
Still furthermore,the triaxial woven fabric and the
non-woven fabric are laminated and thereafter may be plated.
-
Furthermore, the triaxial woven fabric may be a prepreg
impregnated with a resin.
-
Still furthermore, the invention can be applied to the
molded bodies such as the reflector of the parabolic antenna,
the element and ground conductor of the slot antenna, the
element, the ground conductor and a micro-strip line of the
patch antenna, the solar battery paddle of the artificial
satellite, and the bus (structure) of the artificial satellite
and so on.
-
When the molded body is used in, for instance, an antenna
for use in space, an antenna that is storable, expandable, and
high in the performance can be obtained.
Industrial Applicability
-
As explained above, according to the invention, the
following excellent advantages can be achieved.
-
Since the non-woven fabric does not cause the peeling
and the wrinkle, including complicated three-dimensional
shapes, the structure can be freely designed.
-
When the electrical conducting non-woven fabric is used
as the non-woven fabric, in the electrical conducting non-woven
fabric, since kinds of metals and fibers, and the filament
diameters and single fiber diameters can be freely selected,
the electrical conducting properties, the reflectance, the
porosity, the thickness and the weight can be freely
controlled.
-
Furthermore, when a surface of the electrical conducting
non-woven fabric is processed smooth, mirror surface precision
can be improved, resulting in further improving the
reflectance.
-
When the non-woven fabric having the heat conducting
properties is used as the non-woven fabric, a thickness
direction of the molded body in which the composite material
is used such as the antenna reflector can be endowed with the
heat conducting properties.
-
When a heat insulating non-woven fabric is used as the
non-woven fabric, with a simple structure, the temperature
fluctuation in the members of an artificial satellite can be
alleviated.
-
When an electrical insulating non-woven fabric is used
as the non-woven fabric, a layout of circuits and various kinds
of devices on the composite material can be easily designed.
-
Since the triaxial woven fabric is assigned to the
dimension stability and the strength properties and the
non-woven fabric is assigned to the functionality such as the
electrical conducting properties, the reflecting properties,
and the heat conducting properties and so on, by combining the
respective materials and structures, designs appropriate for
applications and conditions can be realized.
-
The triaxial woven fabric and non-woven fabric, being
pseudo-isotropic in planes, are functionally less influenced
by temperature fluctuations and the stress loads. Accordingly,
lighter structural materials can be obtained.
-
The triaxial woven fabric and non-woven fabric, having
void portions therein, can stand up to the sound and vibration
at the rocket launch.
-
According to the invention, the materials most
preferable for the functional structure materials for use with
the artificial satellite that combine the excellent
dimensional stability, the pseudo-isotropy, the light weight,
the high elastic modulus, the high heat conducting properties
and the high reflecting properties can be obtained.
-
Furthermore, since the composite material is formed by
laminating the non-woven fabric having the heat conducting
properties or the heat insulating properties with the triaxial
woven fabric, when the composite material is used, the heat
control can be easily and as far as necessary applied to
necessary portions of the device (for instance, devices for
use with the artificial satellite) according to the existing
manufacturing method.
-
In the triaxial woven fabric, the weave structure
generates hexagonal through holes that interconnect front and
rear surfaces thereof. Accordingly, when the structure where
the electrical conducting non-woven fabrics sandwich the front
and rear surfaces of the triaxial woven fabric is taken, the
electrical conducting non-woven fabrics on the front and rear
surfaces can be mutually electrically connected, and thereby
can be functioned as an electrical conductor of one body.
According to the lamination structure, the mechanical strength
and the electrical characteristics can be accentuated.
-
The invention can be applied to, including electric
circuit substrate, radiation elements, reflecting surfaces
and so on of the various kinds of antennas.
-
According to the invention, the line antennas such as
the parabolic antennas and dipole antennas and so on, or planar
antennas and so on such as patch antennas and so on are excellent
in the electrical properties and very light in the weight, being
high in the elastic modulus to the stress, exhibit the
spring-back function even under large stress to restore its
original shape without undergoing the plastic deformation.
Accordingly, these can be applied under various circumstances.